I wrote a small patch for Mastodon that got accepted yesterday. It lets you set up an email domain whitelist for your instance. For example, if your school wants to set up an instance just for students, they can do it by limiting signups to addresses at `whatever.edu`.
@pete a straight up email whitelist would be useful for if membership is for patreon contributors only, or something like that
@LogicalDash That's a good idea. I wonder if maybe an invite system would work better though? Like an option to make signups "invite only," where an admin has to plug in your email address and you click a link to sign up on an instance.